Earth Glide (Ex)

A burrowing earth elemental can pass through stone,
dirt, or almost any other sort of earth except metal as easily as a fish
swims through water. If protected against fire damage, it can even
glide through lava. Its burrowing leaves behind no tunnel or hole, nor
does it create any ripple or other sign of its presence. A move earth spell cast on an area containing a burrowing earth elemental flings the elemental back 30 feet, stunning the creature for 1 round unless it succeeds on a DC 15 Fortitude save.

Earth Mastery (Ex)

An earth elemental gains a +1 bonus on attack and
damage rolls if both it and its foe are touching the ground. If an
opponent is airborne or waterborne, the elemental takes a –4 penalty on
attack and damage rolls. These modifiers apply to bull rush and overrun
maneuvers, whether the elemental is initiating or resisting these kinds
of attacks. (These modifiers are not included in the statistics block.)

Earth
elementals are plodding, stubborn creatures made of living stone or
earth. When utterly still, they resemble a heap of stone or a small
hill.

When an earth elemental lumbers into action,
its actual appearance can vary, although its statistics remain
identical to other elementals of its size. Most earth elementals look
like terrestrial animals made out of rock, earth, or even crystal, with
glowing gemstones for eyes. Larger earth elementals often have a stony
humanoid appearance. Bits of vegetation frequently grow in the soil that
makes up parts of an earth elemental's body.